1. Field of the Invention
The present invention relates to a suspension, a head supporting mechanism having a combination of the suspension and a support arm, a head arm assembly (HAA) having the head supporting mechanism with a flying type head slider supporting a write and/or a read head element such as a thin-film magnetic head or an optical head, and a disk drive device with the HAA.
2. Description of the Related Art
In a magnetic disk drive device, a thin film magnetic head for writing magnetic information into and/or reading magnetic information from a magnetic disk is in general formed on a magnetic head slider flying in operation above the rotating magnetic disk. The magnetic head slider is fixed at a front end section of an HAA.
The HAA mainly includes a magnetic head slider, a flexure with elasticity supporting the magnetic head slider, a suspension having a load beam with elasticity supporting the flexure at a front end section of itself and a base plate supporting a rear end section of the load beam, and a support arm with high rigidity supporting the suspension. A load applied to the magnetic head slider in a direction to a magnetic disk surface is generated with a leaf spring set at some midpoint of the load beam in the suspension.
The conventional HAA as described above has a cantilever structure supporting the suspension at the rear end section of the structure. The cantilever structure has merits in a stabilization of a load applied to the magnetic head slider and a space saving, however it has a serious problem of a low impact-resistance. In other words, in the cantilever structure, because the magnetic head slider is mounted to a front end section without restraint, a torque applied by the magnetic head slider is added to a torque by the whole cantilever structure. The torque addition causes a slap mode that corresponds to popping-up from the magnetic disk surface or to beating it. Especially, the slap mode has a tendency to occur more often because the load beam, which is a lever structure supporting the magnetic head slider, is formed of a spring material with low rigidity (a stainless steel plate rather thicker than the flexure).
Almost no excessive impact is applied to a magnetic disk drive device with 3.5-inch disk mounted to a computer called high-end or desktop type. However, to a magnetic disk drive device with 2.5-inch disk mounted to a notebook computer, an excessive impact is likely to be applied, so the low impact-resistance becomes a serious problem.
In order to improve the impact-resistance of the HAA, an HAA with a new structure is proposed, where a magnetic head slider is mounted to one end section of an arm with high rigidity, while a coil part of a voice coil motor (VCM) for horizontal rotation is fixed to the other end section, and a balance structure is formed, which makes the arm rotatable in a radius direction of the magnetic disk around a bearing and rotatable in a orthogonal direction to a surface of the magnetic disk around the bearing, then a load is applied to the magnetic head slider by giving a leaf spring set at the bearing a force through a pivot. The proposed structure is described in, for example, U.S. Pat. No. 6,751,064.
According to such an HAA with the balance structure, in case of a magnetic disk drive device with a single small-radius disk such as a micro drive, because a distance between the VCM and the magnetic head slider is small, it is possible to balance the weight between an arm portion in the VCM side on the bearing and the rest arm portion in the magnetic-head-slider side on the bearing. However, because an arm length becomes large in case of a magnetic disk drive device with larger-radius disk such as 1.8-inch or 2.5-inch disk, it is difficult to hold the impact-resistance sufficiently. Further, because the HAA has a structure balanced by the VCM, it is impossible to construct a magnetic disk drive device with a plurality of the HAAs overlapped.
In order to dissolve the above-mentioned disadvantages, the inventors are proposed to provide a balance structure formed at a front end section of the support arm.
FIG. 1 shows a side view for explaining the schematic structure of the HAA proposed by the inventors, and FIG. 2 shows a schematic diagram illustrating the movement of the balance structure of the HAA shown in FIG. 1.
In FIG. 1, reference numeral 10 denotes a support arm, 11 denotes a load beam having a balance structure in which a fulcrum is a protrusion 12 as a load support point fixed to a front end section of the support arm 10, 13 denotes a support spring coupling the load beam 11 to the support arm 10, for giving a force to the load beam 11 through the protrusion 12, 14 denotes a magnetic head slider supported by a front end section of the load beam 11 through a flexure 15, and 16 denotes a magnetic disk, respectively. In the HAA, as shown in FIG. 2, torques of an arm portion in a front side on the load support point 12 and the rest arm portion in a rear side on the load support point 12 are made equaled, which satisfies m1*l1=m2*l2, where m1 is a center of mass of the arm portion in the rear side on the load support point 12, m2 is a center of mass of the rest arm portion in the front side, that is, the magnetic head slider 14 side on the load support point 12, l1 is a distance between the load support point 12 and the center of mass m1, and l2 is a distance between the load support point 12 and the center of mass m2. In other words, a center of gravity in the HAA except a holding part 17 is coincided with the load support point 12.
In the HAA with the above-mentioned structure, because the balance structure is formed at the front end section of the support arm 10 thicker than the load beam 11, a first bend-mode frequency as a characteristic frequency of the structure does not decrease in case that the support arm becomes longer differently from a case that the load beam becomes longer. Therefore, an impact-resistance of the structure does not decrease. Further, because the HAA is not a structure balanced by a coil part of the VCM, it is possible to construct a magnetic disk drive device with a plurality of the HAAs overlapped.
In the HAA having the structure shown in FIG. 1, in order to further enhance the impact-resistance, it is required to heighten the first bend-mode frequency of the load beam without increasing the load beam's weight.
Setting reinforcing parts such as ribs at both side ends of the load beam is well known in the art, and is a effective means for heightening the first bend-mode frequency without increasing the weight. Longer and higher the ribs are, higher becomes the first bend-mode frequency.
However, the ribs cannot be made longer than the whole length of the load beam, and a height limit of the ribs is imposed by need to keep clearance between the HAA and the magnetic disk. Therefore, it is seriously difficult to heighten the first bend-mode frequency in the conventional HAA. Consequently, quite difficult is to enhance the impact-resistance.